1. Field of the Invention
The present invention relates to an airfoil used in a gas turbine engine, either as a rotary blade or a stationary vane, where the metal airfoil includes a layer of a porous foam metal material which varies in density in order to promote heat transfer from the airfoil surface to the fiber metal material, and includes a thermal barrier coating applied on top of the porous foam metal.
2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
Airfoils used in gas turbine engines have used porous metal materials placed between a base metal of the airfoil and a thermal barrier coating to improve heat transfer and cooling of the airfoil. Many types of ceramic and metal porous materials have been used. None, as far as the inventor of the present invention is aware of, disclose the foam material to have varying density.
U.S. Pat. No. 3,619,082 issued to Meginnis on Nov. 9, 1971 shows a turbine rotor blade of laminated porous metal cast into a base and includes an inner reinforcing layer which has increased porosity in the direction span wise of the blades so that the strength diminishes with load in the span wise direction and the porosity provides for flow of air to the porous blade wall. Pores or relieved areas in some sections of some layers are elongate and disposed with their long dimension span wise of the blade for increased strength in direction, in which stress in the blade is greatest. The Meginnis invention does not have variable density porous metal fiber material.
U.S. Pat. No. 4,629,397 issued to Schweitzer on Dec. 16, 1986 shows a gas turbine blade which is coolable for use under high thermal load conditions, has a metallic support core with cooling ducts separated by lands in its surface. The core and its cooling ducts and lands are enclosed by an inner layer of metal felt and an outer layer of heat insulating ceramic material which partially penetrates into the metal felt to form a bonding zone between the felt and the ceramic material. Thus, any heat passing through the ceramic layer is introduced into the large surface area of the metal felt enabling the latter to efficiently introduce the heat into a cooling medium flowing in the ducts, thereby preventing thermal loads from adversely affecting the metal core to any appreciable extent. The Schweitzer invention does not have variable density porous metal fiber material.
U.S. Pat. No. 4,075,364 issued to Panzera on Feb. 21, 1978 and U.S. Pat. No. 4,338,380 issued to Erickson et al on Jul. 6, 1982 show turbine blades with a porous fiber metal applied to a base of the blade, and a thermal barrier coating applied to the porous metal, but the density of the porous metal does not vary.